Using URIs to connect to a MQTT server

URIs are useful to provide serval pieces of information in a single compact string. They can be used to convey all the information required to connect to a MQTT server.

The format is like this:


A typical use for this is to provide the details of a MQTT server in an environment variable. The suggested name for this variable is ‘MQTT_SERVER’.


The scheme part describes the protocol to use to communicate with the server. It can either be ‘mqtt’ for unencrypted communication or ‘mqtts’ to wrap up to MQTT protocol in a secure TLS encrypted connection.

Some implementations may also support the ‘tcp’ and ‘ssl’ scheme names.


The second section of the URI is the username to be put into the CONNECT packet, send directly after opening the socket. If no username is given or it is an empty string, then the user name flag should not be set in the CONNECT packet.


Optionally a password may be given in the URI. This is also passed into the CONNECT packet. A colon separates the username and password. If the username is an empty string, then the password should still be sent.

Host and Domain

Other than the scheme, this the only required component of a MQTT URI. This is the DNS name or IP address of the MQTT server to connect to.


The TCP port of the MQTT server to connect to. If no port is given, then the default port number, 1883, is used for the ‘mqtt’ scheme and port 8883 is used by default for the ‘mqtts’ scheme.

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Harshvardhan Mishra

I am an IoT (Internet of Things) Enthusiast and Blogging is my Passion. Follow and send tweets me on @harshvardhanrvm

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